Pico Systems USC and GSI products

Hello,
I've recently stumbled upon the Pico Systems site, which I believe
is run by Mr. Jon Elson that I see around these cnc boards so often.

I'm interested in the Univ. stepper controller and the Gecko servo
interface. Are these experimental prototypes or reliable, mature
products? The USC in particular has some interesting features like a
300,000 pps pulse generator, E-stop circuit, and what looks to be a
way to close the encoder feedback loop in software. Not to mention a
true DRO, parallel port breakout board and IO board all in one. Why
don't more people use these boards?

Do they only work with Linux EMC, or will they work with Mach2 on
Win XP?

I would like to hear more about these products (in lamens terms)
and how the specific features work with Gecko G320's and/or Rutex
servo drives.

It also looks like there are boards that work with step/dir
software but outputs an analog signal to control AC and DC brushles
servo drives. Here I thought hobby cnc was limited to step/direction
drives and brushed DC servos or steppers.

Is there a way to control a VFD and AC spindle motor with any of
these baords?

Thanks.